The four teenagers who ambushed Sean Patrick Conroy in a subway concourse Wednesday chose their victim at random and attacked him for no other purpose than to amuse themselves, police said yesterday.

"He just happened to be walking in front of them and they picked him out," said Homicide Lt. Melvin Williams.

The District Attorney's Office said Kinta Stanton, 16, of the 4900 block of North Smedley Street in the Logan section of the city, was arraigned yesterday afternoon on murder and conspiracy charges. Officials will seek to try Stanton, a 10th grader at Simon Gratz High School in North Philadelphia with a clean record, as an adult. He was being held without bail.

Police last night were searching for three of his classmates who they said participated in the 2:35 p.m. attack on the Market-Frankford Line concourse at 13th and Market Streets. The four students, police said, were truant from school when they went after the 36-year-old Starbucks manager, who yesterday was described by some who knew him as "cheerful" and "meek and mild."

Police yesterday discounted robbery as a motive, and said the youths apparently launched the attack on a lark.

"I think that's what makes it so horrific, the fact that anybody could have basically been the victim of this type of behavior," said Deputy Police Commissioner Richard Ross.

Although Philadelphia has experienced a 28 percent decline in homicides this year, the death of a commuter during daylight hours in the heart of Center City has stunned officials, and threatened to eclipse the impression that a new mayor and police commissioner were conquering crime.

"This is not Philadelphia," Mayor Nutter said during a visit to the crime scene yesterday. "Bad things, unfortunately, happen in a lot of places. It's a random, stupid act of violence."

Police said Stanton confessed to the assault and told them how he and the three others were heading down the stairs leading to the concourse and the westbound subway when they came upon Conroy from behind. They then struck him on the head and pummeled him, and Conroy fell to his knees, police said.

Authorities said a SEPTA police sergeant on foot patrol on the eastbound side of the concourse heard Conroy scream and witnessed the altercation on the opposite side. By the time he traversed the tracks through a tunnel to get to the westbound side, the assailants had fled. The sergeant attempted to resuscitate Conroy, who had lapsed into unconsciousness from a seizure. Another transit officer, alerted by radio of the attack, arrested Stanton.

Conroy was pronounced dead at Thomas Jefferson University Hospital less than an hour later.

The medical examiner yesterday ruled his death a homicide.

The cause was "asthma, contributed to by blunt force injuries" sustained during the attack, according to Jeff Moran, a coroner's spokesman.

Conroy, manager of the Starbucks at the Philadelphia Marriott Downtown on Market Street, was recalled yesterday as a mild-mannered man who had recently moved into a larger apartment in his South Philadelphia building in anticipation of getting married.

"He never gave me any problem," said Blase Lombardo, who had rented an apartment to Conroy in a triplex in the 1900 block of South 10th Street for the last five years. "He was the kind of guy who paid his rent ahead of time."

"He was always sweet, always smiling, and always nice and cheerful, even when we weren't," said Ana Sofia Santo, a paralegal who remembered Conroy when he managed the Starbucks in the Bellevue on Broad Street before transferring to the Marriott outlet last year.

Acquaintances doubted that Conroy could have provoked the attack.

"He is so low-key, quiet and pleasant," said Ralph Petrone, manager of Rose's Deli at 10th and McKean Streets, near Conroy's residence.

Petrone said Conroy stopped in at the corner grocery frequently to buy a snack cake and soda on his way to work. He usually spoke only when spoken to, he said.

"I'm shocked," said Petrone. "Totally shocked. It was a brutal, brutal murder. I don't understand. He wasn't the kind of guy to attract attention. He was very meek and mild."

A man at Conroy's apartment who identified himself as the victim's father said he was distraught and declined to comment.

The Starbucks outlet was closed yesterday.

"Our thoughts remain focused on the family, friends and colleagues of Sean Conroy, a longtime and well-respected Starbucks employee," the company said in a statement. "This is a tragic incident that has had a significant impact on the many people who knew and worked with Sean."

The brazenness of the assault - a block from City Hall and the Convention Center - unsettled commuters.

"It's appalling," said Khalid Ali, 27, a SEPTA commuter. "I don't know what kind of monsters would brutally do that to a hardworking American."

The attack occurred on the pedestrian concourse, one level below the street surface and one level above the train platforms, according to SEPTA. The station is heavily used by commuters and conventioneers, and is not considered a trouble spot.

City Controller Alan Butkovitz yesterday advised SEPTA that he was launching an inquiry into the agency's deployment of its police force because there was only one officer at the station during the attack.

In an interview last month following several attacks by high school students in the Broad Street Line, SEPTA Police Chief Richard J. Evans said it was virtually impossible for the agency to place an officer in every station and subway car during the combustible after-school hours.

SEPTA spokesman Jim Whitaker said the agency had begun a pilot program to install security cameras in the two subway lines and that eventually every station will be monitored.

"We're in the process of installing a $90 million system, a smart system that will have multiple cameras in each station along with a fire suppression system and emergency systems," said Whitaker. "It's very technically advanced. We hope to have the first phase in place by 2009."

Following the attacks in the Broad Street Line in February, city police dispatched some teams of officers to the subways to reinforce SEPTA's officers.

Deputy Commissioner Ross said he was unprepared to address SEPTA's security, but said Conroy's death "speaks to a bigger issue" about children, family values, and "a whole host of things that are a lot bigger."

"I can't even imagine someone just targeting an individual for nothing, simply because they don't like the way they look or 'I don't have anything better to do,' " said Ross. "To me, that's unconscionable."

Stress and Asthma: Bad Mix

The city Medical Examiner's Office ruled yesterday that the cause of death was "asthma, contributed to by blunt force injuries."

How could that happen?

Many factors can provoke an asthma attack, said Reynold A. Panettieri Jr., director of the asthma program at the University of Pennsylvania. Among them: viruses, allergens, stress and trauma.

While it is possible that blunt force injuries played a role, Panettieri suspects that the extreme stress of the situation and the victim's inability to take his asthma medication during the assault were factors.

Pinning down the cause or causes can be difficult after the fact, said Panettieri, who was not involved in the case. "The airways where asthma resides are pretty deep in the chest . . . but asthma attacks have been associated with car accidents."

Regardless of the actual trigger, the doctor said, the victim was clearly unable to use asthma medication that would have eased bronchospasms that caused the muscles around his airways to restrict his ability to breathe.

- Josh GoldsteinEndText